Garden buildings:

Don't heat but do ventilate.
Solar control blinds.

Conservatories
and Glasshouses:

The conservatory should not
be heated for longer periods or to a higher temperature than
is really necessary.
If your conservatory is not occupied it should always be thermally
isolated from the house.
If long hours of occupancy and a space open to the house are
required, a conventional extension will be much less energy intensive.
The bigger the conservatory, the more heating it will require.
A large conservatory, even if it is only heated to 18°C,
can cost more to heat than the well-insulated modern house it
is attached to.
Make sure that the dwarf walls and base are insulated, and consider
the benefits of specifying low-e glass in the windows and an
improved standard of roof system.
Think about how to keep the conservatory comfortable in summer.
Limit the solar gain using solar control glazing or roof blinds,
and ensure that high rates of passive ventilation can be achieved.

Apropos
-hi tech conservatories in aluminium and glass, made in Ashton
under Lyne.

Carpenter
Oak -based in Totnes,
Devon, their websites has a huge gallery of completed projects
which are great to give some ideas.

Iron
Shirt -low impact fantasy
eco cabins made by Grant Oatley from natural materials (straw
bale, turf roofs), plus home made furniture made from wood or
recycled materials and wood burning stoves made to order. Based
in North Devon, he also takes ommissions for alternative and
innovative artworks and structures.

Willowbank -design and install living willow
structures and sculptures. Also run courses at Ragmans farm in
the Forest of Dean.

Timber Intent
-modern eco friendly timber and tensile fabric outdoor structures
-generally used for public buildings, but they do have small
outdoor "sails" suitable for descked areas.

Garden Offices:

Don't forget that you may need
planning approval to erect an office or workshop in your garden
(see the Government's Planning
Guide for householders), and it will also affect the Council
Tax you pay. However, if you are lucky enough to have a largew
enough plot, then working from home can be one of the most sustainable
things you can do, with the attendant reduction in travel.

A frame Architecture -founded by Jeffrey Dutt following his research
into timber frame building the practice has exhibited its innovative
sustainable garden buildings at Chelsea and other major garden
shows.

Alternative Space
-insulated and sustainable garden rooms made in East Dulwich,
London.

In.It
Studios-brainchild
of an architect and joiner partnership, In.it provide garden
rooms and home offices in Leicester.

Lindahl
Lodge Company -tailor
made summerhouses, garden offices, follies, tree-houses or cabins
individually made in Richmond Upon Thames, Surrey.

the
Orb -spectacular oval
mobile structures suitable for use as garden buildings and holiday
park homes.

O-Pod -somewhay impractical, but fun, the
O-Pod was successfully featured on Dragons Den where the owners
did a deal with Theo Paphitis. They also manufacture the space-pod
in a more conventional rectangular format.